When you say “Add a migration and a field…”
At this point, you haven’t actually explained how one might go about adding a migration. So those of us that are familiar with Ecto and how to do migrations will be able to work this out. However, those that aren’t are likely to be completely stuck. As this is a book about Liveview, not necessarily Ecto, I can’t see how this exercise really helps with learning Liveview